Crop spraying is a widespread method for protecting crops from pests as well as for restricting the growth of other, competing forms of plants such as weeds. In applying a herbicide for restricting the growth of other, competing forms of plants, the herbicide is generally mixed with water or in some cases vegetable oils for discharging the mixture under pressure through a hydraulic nozzle. The mixture is widely dispersed in the form of small droplets. The nozzle is typically provided with one or more apertures through which the herbicide is directed under the control of a valve.
The herbicide is generally applied in a continuous manner along the entire length of each crop row. There are several disadvantages to this approach. First, it is expensive, requiring large amounts of increasingly expensive herbicides. Environmentally it is undesirable and sometimes even dangerous, particularly in those areas where the herbicide after repeated spraying over several years tends to saturate the soil and possibly contaminate ground water. Finally, applying a herbicide to crop plants is undesirable and may be unhealthy not only for the plant itself, but also for those who consume the plant product. The present invention provides an improved crop spraying system which eliminates the aforementioned problems of the prior art.